Textural Analyses of Naturally Deformed Peridotite and Gabbro: Implications for the Interpretation of Geophysical Data and the Rheology of the Lithosphere

研究人员将使用他们新获得的电子背散射衍射（EBSD）系统来测量晶格择优取向（LPO），并分析天然变形橄榄岩和辉长岩的微观结构。 EBSD技术可以提高晶体取向测量的效率，特别是对于具有低对称性的矿物，如斜长石和单斜辉石，使其成为研究实验和自然变形岩石中流变过程的有力工具。研究人员将专注于分析自然变形岩石中保存的微观结构，这些岩石具有良好的约束变形历史。 这项研究将提高我们对控制下地壳和上地幔流变学的过程的理解。具体项目包括：（1）确定了橄榄岩中LPO随应变的演化规律，重点研究了动态重结晶的影响、辉石含量的影响和熔体的作用。该项目的结果将为解释地幔中的地震各向异性提供限制。(2)使用LPOs和粒度分析，以调查的条件下，从位错蠕变扩散蠕变的过渡发生在地质条件下，这个过程中可能的作用，应变局部化。 这一部分的研究成果将对板块边界岩石圈尺度断裂带弱化机制提供约束。（3）将LPO测量与大洋辉长岩显微构造研究相结合，约束地质条件下地壳岩石的粘性。

EAR-0230267HirthThe investigators will use their newly acquired electron backscatter diffraction (EBSD) system to measure lattice preferred orientations (LPO) and analyze microstructures in naturally deformed peridotites and gabbros. The increased efficiency in the measurement of crystal orientations made possible by the EBSD technique, particularly for minerals with low symmetry such as plagioclase and clinopyroxene, makes it a powerful tool to investigate rheological processes in both experimentally and naturally deformed rocks. The investigators will concentrate on the analysis of microstructures preserved in naturally deformed rocks with well-constrained deformation histories. This research will improve our understanding of the processes that control the rheology of both the lower crust and upper mantle. Specific projects include: (1) Determining the evolution of LPO with increasing strain in peridotite, concentrating on the influence of dynamic recrystallization, the effect of pyroxene content and the role of melt. The results of this project will provide constraints on the interpretation of seismic anisotropy in the mantle. (2) Using LPOs and grain size analyses to investigate conditions where a transition from dislocation creep to diffusion creep occurs under geologic conditions, and the possible role this process has in strain localization. The results of this part of the project will provide constraints on the mechanisms responsible for weakening lithospheric-scale fault zones at plate boundaries (3) Combining measurement of LPO with microstructural studies on oceanic gabbros to constrain the viscosity of lower crustal rocks under geologic conditions.